Additional chat-related features and issues within Microsoft Teams for business
The primary issue for me is using the web client when someone is screen-sharing.
Screen-sharing pushes all the videos to the top of the page and then this pop-up that you can't get rid of floats over the top of the videos, so I can no longer see anyone.
And in contrast to someone else's suggestion, Ctrl+Shift+M doesn't stop the pop-up from appearing.